cudax::stream::wait() blocks the caller, while cudax::stream::wait(event_ref) does not

[brycelelbach]

cudax::stream A, B;

auto e = A.record_event();

A.wait();
// Block the calling host thread.
// Equivalent to: `cudaStreamSynchronize`.  

B.wait(e);
// Does NOT block the calling host thread.
// Equivalent to: `cudaStreamWaitEvent`.

cudax::stream::wait has three overloads:

• wait(), which blocks the caller until the stream's work is complete.
• wait(event_ref), which makes the stream wait for the event before completing any other work. This does not block.
• wait(stream_ref), which makes the stream wait for the stream before completing any other work. This does not block.

All the functions in well-designed function overload set should:

• Perform the same fundamental operation, perhaps with different configurations, kinds of inputs, and
• Provide the same contract.
  • Identical parameters should have the same constness and mutability.
  • Any semantics that can have subtle and hazardous implications should be identical: allocation, algorithmic complexity, and synchronization.

The wait(event_ref) and wait(stream_ref) functions need a different name. In Thrust's unique_stream I believe I called these depend_on.

[leofang]

This is really a bad name for people who have some basic knowledge in CUDA:

A.wait();

Can we just call it A.synchronize(); or A.sync(); (matching cuda.core)?